I used to get this popping up on mine the odd time, usually if I’d used one of the Google free advertising vouchers that they sent out from time to time.
It’s nothing to worry about if you don’t want it to be, it’s really just Google trying to encourage you to be a bit more organised:)
I did it when I remembered to, but not all the time.
Basically instead of promoting willy nilly you can create a url using their generator for each specific aspect of your promotional efforts so that at the end of the day you can very easily tell what worked and what didn’t.
It’s handy if, for talk sake, you’re paying for advertising on Facebook while still pootling away on your facebook page. Instead of seeing xx visits from facebook at the end of the day with no real way of telling which were as a result of paid advertising and which came from your own efforts, you can create two campaign urls, one to use yourself and one to give to the advertiser you’re paying, they both look the same but google analytics can tell them apart.
The same goes for google, if you’re paying for a bit of advertising, create a url for it so you can tell the difference between those hits and those coming from organic search.
Chances are you’ve had a flood of visitors from one place and analytics is assumimg it’s a campaign but isn’t sure and it’s nudging you to set one up:)